Treating fabrics

Abstract

A method for preshrinking tubular knit fabrics in which the fabric is treated as a continuous length in tubular form. The elongated tube is continuously fed lengthwise into a series of liquid baths which include a wetting agent, scouring and washing constituents and rinses and any finish is to be applied to the fabric. The fabric tube is caused to advance into and through the bath in a substantially tensionless state by pushing the fabric into the flow of liquid and through the bath to avoid applying substantial tension. From the washing and rinsing baths, the saturated fabric is flattened, again without application of substantial tension, and is fed through a two-stage dryer. In the initial stage, the fabric is air-dried to a moisture content of substantially less than 40%. Before introducing the fabric into the second stage of the dryer, the moisture content is raised, for example in a steam atmosphere, to substantially 40%. The final drying is performed in multiple steps to assure uniform treatment of the fabric throughout its length to ultimately reduce the moisture content in the fabric to less than 8%. The illustrated combination of apparatus for accomplishing the fabric treatment includes a relaxing and washing washing range, for the liquid treatment of the fabric, a padding apparatus for the flattening of the fabric while saturated, a drum-type air dryer for air-drying the fabric in the first stage, a steam chest intermediate stage in advance of the final dryer stage, and a tumble-type compartmentalized continuous length dryer in the final stage.

I claim: 
     
       1. A method for pre-shrinking tubular knit fabrics comprising at least 40% cotton comprising the steps of: forming the fabric into an elongated tube, continuously feeding the tube lengthwise into a first bath of liquid, and retaining each part of the tube in the bath of liquid for a sufficient length of time to completely saturate the fabric of the tube;   continuously withdrawing the tube from said first bath and feeding it longitudinally into a sequence of baths by positively feeding the tube into the bath at its entrance end, maintaining said tube immersed in said bath throughout its length, withdrawing said fabric from the opposite end of each bath section by continuously withdrawing the fabric vertically from the discharge end and transferring it, without substantial stretching to the entrance end of the next bath section for positive feeding of the fabric into the next bath section;   controlling the feed and discharge of the fabric to avoid longitudinal stress on the tube during its travel through the bath section, assuring longitudinal compression or slackening of the fabric in its travel through each section;   thereafter arranging said length of tubular fabric into a flattened tubular shape having only two fabric thicknesses throughout;   maintaining said fabric saturated with liquid throughout said arranging step;   feeding said flattened tube into a dryer so as to reduce the moisture content to a range of 20-40% moisture content;   thereafter subjecting the fabric to heat and moisture to stabilize its moisture content in the range of 35-45%; and   feeding the continuous length of fabric into a tumble dryer section and causing the fabric to be repeatedly impacted while slack and removed from longitudinal tension, and while subjected to heat and dry air and continuing the treatment in the tumble dryer for a period to reduce the residual shrinkage of the fabric to less than 8%.   
     
     
       2. A method according to claim 1 wherein said tube is positioned in said baths in a series of folds doubled back on themselves so as to occupy a substantial part of the height and width of the liquid in said bath. 
     
     
       3. A method according to claim 1 wherein the immersion of said tube in said sequence of baths is maintained for a time period to assure thorough saturation of the fabric and its constituent yarns to enable the cotton fibers in said constituent yarns to become saturated and swell, thereby relieving any residual stresses imparted to said yarns during the previous operations in which said fibers are formed into yarns and said yarns are formed into a fabric. 
     
     
       4. A method according to claim 3 wherein at least one of said baths includes a fabric softener to enhance the stress relief, and said time period is approximately 120 minutes. 
     
     
       5. A method according to claim 1 wherein the step of maintaining said tube immersed is achieved by providing oscillating immersion bars adjacent the upper surfaces of said baths in said sequence, and feeding said tube into said baths beneath said oscillating immersion bars. 
     
     
       6. A method according to claim 1 wherein said transfer of the fabric tube from the discharge end of one bath section to the entrance end of the next bath section is effected by providing a closed conduit between said discharge end and said entrance end, spraying a liquid carrier medium into the entrance end of said conduit through an annular jet at a rate of flow to assure liquid flow through the conduit at a linear rate higher than the rate of feed of the fabric tube, and causing said tube to pass axially the center of said annular jet so as to be carried by the liquid flow through said closed conduit. 
     
     
       7. A method according to claim 6 wherein said liquid carrier medium sprayed through said jet is supplied from the liquid in a bath section which is subsequent to the conduit. 
     
     
       8. A method according to claim 1 wherein the initial baths in said sequence of bath sections include scouring components to scour the fabric to remove oils and waxes and foreign matter entrained in the fabric, and the final baths in said sequence rinse the fabric to remove the scouring compositions. 
     
     
       9. A method according to claim 1 wherein said step of stabilizing the moisture content of the fabric in advance of the tumble dryer section comprises the step of depositing the fabric on a conveyor, advancing the conveyor through a closed chamber and spraying a mist of water against the fabric on the conveyor in an atmosphere of steam in the closed chamber to thereby stabilize its moisture content. 
     
     
       10. A method according to claim 1 wherein the fabric is conveyed on a slotted conveyor in said tumble dryer section and hot and dry air is blown upwardly through said conveyor to lift the fabric up from the conveyor. 
     
     
       11. A method according to claim 10 wherein said slotted conveyor travels below saw-toothed baffle plates fixed adjacent said conveyor so that the lifted fabric impinges against said baffle plates. 
     
     
       12. A method for pre-shrinking thermal knit fabrics characterized by air-entrapping cells on one or both sides in longitudinal and transverse rows and comprising at least 40% cotton comprising the steps of: forming the fabric having a given longitudinal cell count into an elongated tube, continuously feeding the tube lengthwise into a first bath of liquid, and retaining each part of the tube in the bath of liquid for a sufficient length of time to completely saturate the fabric of the tube and cause the longitudinal cell count to increase;   continuously withdrawing the tube from said first bath and feeding it longitudinally into a sequence of baths by positively feeding the tube into the bath at its entrance end, maintaining said tube immersed in said bath throughout its length, withdrawing said fabric from the opposite end of each bath section by continuously withdrawing the fabric vertically from the discharge end and transferring it, without substantial stretching to the entrance end of the next bath section for positive feeding of the fabric into the next bath section without reducing the longitudinal cell count;   controlling the feed and discharge of the fabric to avoid longitudinal stress on the tube during its travel through the bath section, assuring longitudinal compression or slackening of the fabric in its travel through each section;   thereafter arranging said length of tubular fabric into a flattened tubular shape having only two fabric thicknesses throughout;   maintaining said fabric saturated with liquid throughout said arranging step and maintaining the longitudinal cell count of the saturated fabric not substantially less than the longitudinal cell count prior to flattening;   feeding said flattened tube into a dryer so as to reduce the moisture content to a range of 20-40% moisture content without substantially reducing the longitudinal count;   thereafter subjecting the fabric to heat and moisture to stabilize its moisture content in the range of 35-45%; and   feeding the continuous length of fabric into a tumble dryer section and causing the fabric to be repeatedly impacted while slack and removed from longitudinal tension, and while subjected to heat and dry air and continuing the treatment in the tumble dryer for a period sufficient to increase the longitudinal cell count and to reduce the residual shrinkage of the fabric to less than 8%.   
     
     
       13. Apparatus for preshrinking tubular knit fabrics comprising at least 40% cotton, said apparatus comprising in combination: a J-box for receiving the fabric in elongated tubular form having an upright receiving leg and a curved bottom, means to feed the fabric into a curved bottom through said upright leg and means to wet the fabric with a liquid in said upright leg, said liquid collecting in said curved bottom to a height above the level of the fabric in the curved bottom to enable the fabric to be totally immersed and become saturated with the liquid;   a relaxing and washing range connected to said J-box having an inlet tank to receive the fabric from said curved bottom of the J-box and a series of elongated baths with means to feed the fabric sequentially through said baths, said fabric feeding means for each bath comprising a tubular conduit having an inlet portal forming an annular jet for the introduction of conveying liquid into the center of the conduit in an annular spray directed generally longitudinally of the conduit, and means to feed the fabric into the center of said portal so as to be introduced into the flow of liquid from said annular jet, the opposite end of said conduit directing the fabric into one end of the associated bath, said bath having holddown bars to maintain the tubular material submerged within said bath, said bath at the opposite end adapted to discharge the fabric into a receiving tank underlying the inlet portal of the conduit for the next bath in said series, whereby the fabric may be lifted into the portal from said receiving tank, and means to discharge the fabric from the receiving tank of the last bath in said series in a saturated state;   an extracting apparatus operable to receive the fabric from the discharge means of said relaxing and washing range to straighten the fabric and flatten it into open-width configuration and having means to maintain the fabric saturated while it is straightened and flattened, and means to extract free moisture from said saturated fabric, said apparatus including feed rolls to advance the fabric through the apparatus at a rate to maintain the longitudinal stitch count of the fabric substantially the same at the entrance and exit ends of said extracting apparatus;   an air dryer operable to receive the fabric from said extracting apparatus, said air dryer including means to support and convey the fabric through the dryer in a relaxed state without application of substantial longitudinal tension and means to discharge dry and hot air against and through the fabric to reduce its moisture content to less than 40%;   a steam chest having a foraminous conveyor and misting sprays to receive the fabric from the hot air dryer and to convey the fabric on said conveyor past said sprays while on the conveyor, said steam chest having control means providing a controlled steam atmosphere to stabilize the fabric exiting the steam chest at a moisture content of 40%; and   a continuous tumble dryer to receive the stabilized fabric from the steam chest, said tumble dryer including a series of dryer sections with a foraminous conveyor for conveying the fabrics sequentially through said sections, means to deposit the fabric on the conveyor at the entrance end of said tumble dryer in loose folds and means in each section to supply and impinge air against the fabric with a sufficient force to cause the fabric on the conveyor to tumble within each section of said series, and means to control the heat and humidity of the air supplied in each section, to thereby control the dryness of the fabric within each section, said apparatus discharging the fabric at a uniform dryness in the range of 6-10%.